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  • 1985-1989  (4)
Document type
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Dynamics of Protistan Carbon and Nutrient Cycling, (1988)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 35 (1988), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1988.tb04335.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Grazing of attached bacteria by heterotrophic microflagellates (1987)
    Springer
    Microbial ecology 13 (1987), S. 203-218 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four species of heterotrophic microflagellates were examined for their ability to graze attached and unattached bacteria. The species tested displayed pronounced differences in their ability to graze the bacteriumPseudomonas halodurans attached to chitin particles. Two species of microflagellates (Monas andCryptobia sp.) efficiently grazed unattached bacteria but showed little or no ability to graze attached or aggregated cells. In contrast,Rhynchomonas nasuta andBodo sp. showed marked preferences for attached and aggregated bacteria and a limited ability to graze unattached cells. The density of attached bacteria was reduced by an order of magnitude due to grazing byBodo andR. nasuta, even though the density of unattached bacteria was ∼5–90× the density of attached cells. The maximum densities attained by microflagellates in the cultures were related to the density of unattached bacteria forMonas andCryptobia but not forBodo andR. nasuta. Growth of the latter two species appeared to be related to the density of attached or aggregated bacteria. Based on the results of these experiments, it is concluded that the pelagic existence of microflagellates that graze attached bacteria may be strongly linked to the distribution of suspended particles and their associated bacteria. In addition, the removal of attached bacteria by microflagellates can significantly affect the density of bacteria attached to particles in the plankton. This activity may have important implications for the controversy concerning the relative importance of attached and free-living bacteria in the plankton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02024998
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Factors responsible for the differences in cultural estimates and direct microscopical counts of populations of bacterivorous nanoflagellates (1989)
    Springer
    Microbial ecology 18 (1989), S. 89-104 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bacterivorous nanoflagellates (microflagellates) have been routinely enumerated in marine and freshwater samples using either a Most Probable Number (MPN) culture method or by a direct microscopical counting method (DC). These two techniques typically yield highly disparate estimates of the density of nanoflagellates in natural samples. We compared these methods with seawater and marine snow (macroscopic detrital aggregate) samples collected from surface waters throughout the North Atlantic and in freshwater samples collected at three stations in Lake Ontario. Densities of nanoflagellates determined by the two methods differed by as much as four orders of magnitude; the MPN estimate rarely exceeded 10% of the microscopical count, and averaged ≈ 1% of this count. The MPN estimate constituted a higher percentage of the DC value in environments with high concentrations of nanoflagellates relative to environments with low concentrations of nanoflagellates. The ratio of the culture count to the microscopical count (MPN∶DC) increased along an environmental gradient from oligotrophy to eutrophy, and was positively correlated with the density of bacteria in the samples. In laboratory experiments with two species of bacterivorous nanoflagellates, the MPN count constituted a much greater percentage of the DC count during the exponential growth phase of the nanoflagellate than during the stationary growth phase. Differences in the estimates of nanoflagellate density obtained with these two techniques probably can be explained by the trophic mode of these protozoa, their growth stage, and the amenability of these species to laboratory culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02030118
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental demonstration of the roles of bacteria and bacterivorous protozoa in plankton nutrient cycles (1988)
    Springer
    Hydrobiologia 159 (1988), S. 27-40 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have used a model food chain composed of a natural bacterial assemblage, a pennate diatom and a bacterivorous microflagellate to investigate the factors controlling the relative importance of bacteria and protozoa as sources for regenerated nitrogen in plankton communities. In bacterized diatom cultures in which diatom growth was nitrogen-limited, the carbon:nitrogen (C:N) ratio of the bacterial substrate greatly affected which population was responsible for the uptake of nitrogen. When nitrogen was added as NH 4 + and the cultures were supplemented with glucose, the bacteria competed successfully with the algae for NH 4 + and prevented the growth of algae by rapidly assimilating all NH 4 + in the cultures. Bacterivorous protozoa inoculated into these cultures grazed the bacterial population and remineralized NH 4 + , thus relieving the nitrogen limitation of algal growth and allowing an increase in algal biomass. In contrast, bacteria in cultures supplemented with the amino acid glycine (C:N = 2) were major remineralizers of nitrogen, and the influence of protozoan grazing was minimal. We conclude that the relative importance of bacteria and protozoa as nutrient regenerators in the detrital food loop is dependent largely on the overall carbon:nutrient ratio of the bacterial substrate. The role of bacterivorous protozoa as remineralizers of a growth-limiting nutrient is maximal in situations where the carbon:nutrient ratio of the bacterial substrate is high.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007365
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    Paper (German National Licenses)
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